Simulation of Reciprocal Space Maps for Thin Ion-Implanted Layers in Yttrium-Iron Garnet Films with Defects

Numerical simulation of the reciprocal space maps measured from the ion-implanted single-crystal yttrium-iron garnet films on gadolinium-gallium garnet substrate has been carried out basing on the theoretical model of the triple-crystal dynamical diffractometry of crystalline multilayer systems with inhomogeneous strain distributions and randomly distributed defects. The presence of growth defects in both film and substrate as well as radiation defects created in subsurface layer of nanometer-scale thickness after 90 keV F+ ion implantation was taken into account in the proposed model of the film system

Dynamical X-Ray Diffraction Characterization of the Self-Organized Quantum Dot Formation In Imperfect Semiconductor Superlattices

The self-organized quantum dot (QD) formation in InGaAs/GaAs superlattices grown by molecular beam epitaxy was investigated by the high-resolution X-ray diffraction technique. The investigated samples had the identical structure consisting of fifteen periods of {InxGa1−xAs (8 ML)/GaAs (26 ML)} with the nominal In concentration x = 0.2. The diffraction profiles and reciprocal lattice maps for these samples have been measured at symmetrical (004) reflection by using the triple-crystal X-ray diffractometer. The analysis of the measured data was performed by using the proposed diffraction model based on the statistical theory of dynamical X-ray scattering in imperfect single crystals and multilayer structures

Simulation of Reciprocal Space Maps for Thin Ion-Implanted Layers in Yttrium-Iron Garnet Films with Defects

Numerical simulation of the reciprocal space maps measured from the ion-implanted single-crystal yttrium-iron garnet films on gadolinium-gallium garnet substrate has been carried out basing on the theoretical model of the triple-crystal dynamical diffractometry of crystalline multilayer systems with inhomogeneous strain distributions and randomly distributed defects. The presence of growth defects in both film and substrate as well as radiation defects created in subsurface layer of nanometer-scale thickness after 90 keV F+ ion implantation was taken into account in the proposed model of the film system

Transformations of microdefect structure in silicon crystals under the influence of weak magnetic field

Quantitative characterization of complex microdefect structures in annealed silicon crystals (1150 °С, 40 h) and their transformations after exposing for one day in a weak magnetic field (1 T) has been performed by analyzing the rocking curves, which have been measured by a high-resolution double-crystal X-ray diffractometer. Based on the characterization results, which have been obtained by using the formulas of the dynamical theory of X-ray diffraction by imperfect crystals with randomly distributed microdefects of several types, the concentrations and average sizes of oxygen precipitates and dislocation loops after imposing the magnetic field and their dependences on time after its removing have been determined

Structural changes in multilayer systems containing InxGa₁₋xAs₁₋yNy quantum wells

The investigations of multilayer nano-scale systems contained one or two quantum wells are carried out by double-crystal X-ray diffractometry. Processes of interdiffusion of In, Ga atoms and their influence on properties of such systems are considered. The content of nitrogen in quantum wells and buffer layers are defined. It is determined that InxGa₁₋xAs₁₋yNy system has perfect crystalline structure, and interface between layers is coherent

X-Ray Diffraction Characterization of Nanoscale Strains and Defects in Yttrium Iron Garnet Films Implanted with Fluorine Ions

The theoretical diffraction model for a crystalline multilayer system with inhomogeneous strain profile and randomly distributed defects has been created by using the statistical dynamical theory of X-ray diffraction in imperfect crystals. The dynamical scattering peculiarities in both coherent and diffuse scattering intensities have been taken into account for all the layers of the system by using derived recurrence relations between coherent scattering amplitudes. The investigated yttrium-iron garnet films grown on gadolinium-gallium garnet substrate were implanted with different doses of 90 keV F+ ions. The rocking curves measured from the as-grown and implanted samples have been treated by using the proposed theoretical model. This model has allowed for the reliable self-consistent determination of strain profile parameters and structural defect characteristics in both implanted film and substrate of the investigated samples

Double- and triple-crystal X-ray diffractometry of microdefects in silicon

The generalized dynamical theory of X-ray scattering by real single crystals allows to self-consistently describe intensities of coherent and diffuse scattering measured by double- and triple-crystal diffractometers (DCD and TCD) from single crystals with defects in crystal bulk and with strained subsurface layers. Being based on this theory, we offer the combined DCD+TCD method that exhibits the higher sensitivity to defect structures with wide size distributions as compared with any of these methods alone. In the investigated Czochralski-grown silicon crystals, the sizes and concentrations of small oxygen precipitates as well as small and large dislocation loops have been determined using this method

Models of Deformation Dependences of Total Integrated Intensity of Dynamical Diffraction in Single Crystals for Various Diffraction Conditions

В работе с помощью теории Чуховского—Петрашеня для деформационной зависимости (ДЗ) интегральной интенсивности динамической дифракции (ИИДД) в кристаллах без дефектов показан характер изменения ДЗ ИИДД с толщиной кристаллов и с вариацией других условий дифракции. На этой основе, а также при использовании ряда экспериментов с реальными дефектными кристаллами и результатов теории полной интегральной интенсивности динамической дифракции (ПИИДД) в кристаллах с дефектами без изгиба построена аналитическая модель ДЗ ПИИДД в кристаллах с дефектами, пригодная для диагностики параметров структурных дефектов в кристаллах.В роботі за допомогою теорії Чуховського—Петрашеня для деформаційної залежности (ДЗ) інтеґральної інтенсивности динамічної дифракції (ІІДД) у кристалах без дефектів показано характер зміни ДЗ ІІДД із товщиною кристалу та з варіяцією інших умов дифракції. На цій основі, а також при використанні ряду експериментів із реальними дефектними кристалами і результатів теорії повної інтеґральної інтенсивности динамічної дифракції (ПІІДД) у кристалах з дефектами без вигину побудовано аналітичну модель ДЗ ПІІДД у кристалах з дефектами, придатну для діягностики параметрів структурних дефектів у кристалах.The paper shows the pattern of change in the deformation dependences (DD) of integrated intensity of dynamical diffraction (IIDD) with crystal thickness and with variation of other diffraction conditions by means of the Chukhovskii—Petrashen theory for the DD of IIDD in defect-free crystals. Relying on this and numerous other experiments with real defective crystals as well as the results of total integrated intensity of dynamical diffraction (TIIDD) in crystals with defects without bend, an analytical model of the DD of TIIDD in crystals with defects is developed, which is feasible for the diagnostics of structural defects in crystals

Complex diffractometrical investigation of structural and compositional irregularities in GaAs:Si/GaAs films heavily doped with silicon

Complex of X-ray diffractometrical investigations, both angular and spectral dependences of a reflectivity for quasi-forbidden reflections, enable not only to discover structural microdefects and to measure their radii r as well as concentration n, but also to determine the level of nonstoichiometry, , where are concentrations of lattice components A and B, respectively. In the case of angular dependencies, the two-dimensional maps of diffuse scattering in a reciprocal space for a characteristic radiation were plotted for GaAs:Si/GaAs films heavily doped by Si (up to 10²⁰ cm⁻³) using a three-crystal spectrometer (TCS). In the case of spectral (energy) dependencies, reflectivity were measured using a single crystal spectrometer (SCS) and white beam radiation. In both cases the formulae of the Molodkin dynamical scattering theory developed for real crystals with homogeneously distributed microdefects were used by the fitting procedure of the calculated intensities to those measured using TCS or SCS for (200) and (400) reflections of X-rays. The TCS maps were registred for Cu Ka - radiation by the Phillips three-crystal diffractometer. Good agreement between the two groups of the and parameters of microdefects (precipita¬tes) was shown for some GaAs film (r₁ = 3.5 mm, n₁ = 4.3*10⁶ cm⁻³; r₂ = 4.8 μm, n₂ = 9.4*10⁶ cm⁻³) . Parameter D = 0.009 (Ga excess) was determined too